SUDO AIX

Hi,
I am fairly new to sudo and would like a little advice to what should
hopefully be an easy question. Firstly, I have installed the latest version
of sudo onto AIX 4.3.3.
How can I ensure that users use 'sudo' in front of every command they issue.
For example, a user could issue the following command su - oracle, but I
need to ensure that they use sudo su - oracle.
Thanks
Russell Whiting
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